1. Field of the Invention
The invention relates to a liquid pharmaceutical preparation for the local treatment of psoriasis containing known antipsoriatic active ingredients, in which the medicines therapeutically take effect from a film located on the affected skin area.
2. Discussion of the Background
In treating psoriasis, a dermatosis of yet unexplained origin, one is generally instructed to apply drugs topically such as salicylic acid, vitamin A-acid, glucocorticoids, and more recently with relatively good success, dithranol (1,8,9-anthracenetriol) or acyl derivatives thereof. The formulations to be used are limited to the most common preparations such as, for example, solutions, creams, and salves, in which the manner of application for the dermatherapy is practically predetermined. The use of the therapeutic preparations which generally contain some fat, such as dithranol-salicyclic acid vaseline, a paste-like preparation, are very time consuming for the patients and involve more difficult procedures. Large surface area applications can therefore be preformed only on inpatients, and involves soiling large amounts of laundry and clothing.
By combining the use of urea and the application of dithranol, as according to EP-A No. 6,724, the psoriasis therapy is improved. Preparations of this kind, having for example 0.1% dithranol in a 17% urea salve base, are known, i.e., Psoradrate (see D.M. Wiliamson in Clin. Exp. Dermatol., vol. 8, pp. 287-290 (1983)). Urea, which is known for its keratolytic characteristics, disrupts the epidermis for a more rapid and therefore more effective penetration of the active drug.
In treating particularly resistant strains of psoriasis, the locations which are coated with salve, are covered with waterproof bandages. A sealed moist chamber is thus formed which allows the skin to swell and facilitates penetration of the medicine into the deeper layers.
Medicated self-adhering plasters containing medicines may also be used. To allow for better skin respiration, they are usually perforated and applied to an elastic material. See Ulmanns Encyclopedia of Technical Chemistry, 4th Ed., vol. 4, pp. 24-26. Non-perforated self-adhering bandages for topical therapy with glucocorticoids are known in the form of foils containing the halogenated corticoid fluorandrenolone and having an adhesive layer.
Polymer films containing anthraline (dithranol) or anthraline derivatives as medicines for treating skin injuries such as psoriasis, are disclosed in French Pat. No. 2,515,045. These films are manufactured prior to use from an appropriate solution by being cast in a teflon mold and dried for 15 hours. Molded elements of this type are difficult to apply to affected skin areas.
A more direct method of producing a medicated film on the skin for transdermal application is described in Japanese Kokai Tokkyo Koho 60 16922 (Chem. Abstr. 102, 226041a). According to this reference, a viscous solution containing the pharmaceutical materials is applied to the skin which is then sprayed together with a film-forming polymer solution. This two-stage method for constructing a topical therapeutic system is very awkward, however, and is difficult to accept as a long, extended therapy for the patient.